a) Field of the Invention
The present invention relates to a compact pump comprising a diaphragm portion composing a pump chamber and a valve body disposed in a valve chamber which are integrated with each other.
b) Description of the Prior Art
A conventional compact pump having a diaphragm which is, for example, of a type having three pump chambers has a configuration shown in FIGS. 1 through 4.
In FIG. 1, a reference numeral 1 represents a compact DC motor, a reference numeral 2 designates an output shaft of the motor 1, a reference numeral 3 denotes a case which is formed in a cup shape having a bottom surface attached to a side surface of an output shaft of the motor 1 with screws 4, a reference numeral 5 represents a collar fixed to the output shaft 2, a reference numeral 6 designates a driving shaft which is fixed to the collar 5 so that it is inclined at a predetermined angle relative to the output shaft 2 and its tip is located on a center axis of the output shaft 2, a reference numeral 7 denotes a driving body having a hole 8, a reference numeral 9 represents a cylindrical support portion which is formed integrally with the driving body 7 so as to extend downward from its center, and a reference numeral 10 designates a steel ball which is used to reduce friction between the driving shaft 6 and the driving body 7. The support portion 9 is loosely fitted over the driving shaft 6 and when the output shaft 2 rotates, the driving shaft 6 is rotated in an inclined condition, whereby a peripheral portion having the hole of the driving body 7 reciprocally moves up and down relative to the center of the driving body 7. A reference numeral 11 denotes a cylinder portion which is composed, for example, by forming three holes 12 in a plate like member as shown in FIG. 2, fixing three cylinders to these holes and forming three holes 13.
A reference numeral 14 represents a diaphragm body made of a soft rubber, a reference numeral 15 designates three diaphragm portions having a form of hanging bells which are disposed at intervals of 120 degrees, integrated with one another and extended from the diaphragm body 14, a reference numeral 16 denotes a driving portion located at a center of the diaphragm portion, a reference numeral 17 represents a head portion which is formed at a tip of the driving portion 16 by way of a thin neck portion, and a reference numeral 18 designates a valve body portion which is formed integrally with the diaphragm body so as to extend upward from its center and has, for example, a cylindrical form. The head portion 17 runs through the hole 8 of the driving body 7 and extrudes from a bottom surface of the driving body 7, whereby the driving portion 16 is sustained by the driving body 7. At locations corresponding to the holes 13 in the cylinder portion 11 (see FIG. 2), holes 19 are similarly formed in the diaphragm body 14 (see FIG. 3).
The diaphragm body 14 described above consists of the three diaphragm portions 15, the valve portion 18 and other portions which are integrated with one another and made of an elastic material such as rubber.
A reference numeral 20 represents a lid body which serves also as a valve housing as shown in FIG. 4, a reference numeral 22 designates a hole which is formed to affix a valve, a reference numeral 23 denotes six air suction holes which are formed around the hole 22, a reference numeral 24 represents a valve chamber portion which is formed upward over a center of the lid body 20 and a reference numeral 25 designates an exhaust hole which is formed in a thinned tip of the valve chamber portion 24.
As shown in FIG. 1, the lid body 20 is combined with the cylinder portion 11 with the diaphragm body 14 interposed, and fixed to the case 3 with screws 27 utilizing the holes 26 formed in the lid body 20, the holes 13 formed in the cylinder portion 11 and the holes 19 formed in the diaphragm body 14 so that three pump chambers 28 are formed by the lid body 20 and the diaphragm portions 15.
The lid body 20 has a common chamber 29 which is formed in the valve chamber portion 24 and notch-shaped grooves 30 which are formed inside (toward a center of the lid body) the circumferential portions of the air suction holes 23 (circumferences of portions at which the pump chambers 28 are located) so as to communicate with the common chamber 29. Accordingly, the pump chambers 28 are communicated at centers thereof commonly to the common chamber 29. Furthermore, the valve body portion 18 is in contact with an inner circumferential surface of the valve chamber portion 24 so as to close communication paths.
A reference numeral 31 represents a valve body which is made of a soft rubber and has a shape of an umbrella, a reference numeral 32 designates a pole brace which is formed integrally with the valve body 31 so as to extend upward from its center, a reference numeral 33 denotes a head which is formed on a tip of the pole brace 32 so as to have a diameter larger than that of the pole brace. The valve body 31 is formed so as to have a size large enough to cover the air suction holes 23 and the pole brace 32 passes through the hole 22 so that the head 33 is located outside and will not come off the lid body 20.
Now, description will be made of operations of the compact pump which is configured as described above. When the motor 1 is electrically energized and the output shaft 2 is rotated, the driving shaft 6 is also rotated, whereby points at ends of the outer circumferential surface of the driving body 7 sequentially move up and down to vibrate the driving portions 16 of the diaphragm portions 15 in a vertical direction with a phase difference of 120 degrees. That is, the diaphragm portions 15 make piston movements in the cylinder. The piston movements of the diaphragm portions periodically vary volumes of the pump chambers 28. When the driving portion 16 moves downward and the volume is increased, an internal pressure of the pump chamber 28 is lowered, whereby the valve body portion 18 closes as it is brought into contact with the valve chamber portion 24, whereas the valve body 31 opens to introduce air through the air suction holes 23. When the driving portion 16 moves upward and the volume is reduced at the next stage, the internal pressure of the pump chamber 18 is enhanced, whereby the valve body 31 closes as it is brought into close contact with the lid body 20, whereas the valve body portion 18 which closes the groove 30 of the pump chamber is opened to exhaust air from the pump chamber through the groove 30, the common chamber 29 and the exhaust port 25, from the pump chamber 28 through the common chamber 29 and the exhaust port 25.
This compact pump performs a pump function by operating the three diaphragm portions so as to repeat the movements described above with the definite phase difference, thereby suctioning air through the separate air suction holes 23 and exhausting the air through the common valve chamber 29 and the exhaust port 25.
The diaphragm pump which has the configuration described above combines the case 3 accommodating the driving portion which consists of the collar 5 attached to the output shaft 2 of the motor, the drive shaft 6, the driving body 7, etc. with the cylinder portion 11, the diaphragm body 14 and the lid body (valve housing) 20, and fixes these members as a whole with the screws. Furthermore, the case 3, cylinder portion 11, lid body 20, etc. are made of a synthetic resin material and these members which are made of the synthetic resin material are fixed with metallic screws. Accordingly, each of these members made of the synthetic resin material expands with a coefficient of expansion larger than that of the metallic screws and is deformed at portions fixed with the screws and surroundings thereof in particular when it is heated by operation of the pump and rise of ambient temperature. When temperature lowers after stopping operation of the pump or the expanded case and other members are cooled for a cause, in contrast, they are contracted and resume their initial conditions.
When temperature is raised and lowered repeatedly as described above, the screws are loosened, thereby causing air leakage in some cases.
FIG. 5 is schematic diagram showing locations, etc. of diaphragm portions 15 arranged in a pump which has two diaphragm portions (pump chambers). Since tapped holes are formed at locations indicated by a reference numeral 37, the pump requires spaces for affixing it with screws utilizing the tapped holes, or such excessive spaces for affixing the pump with screws 27 as shown in FIG. 6. Similarly, FIG. 7 shows an outline of a pump which has a single diaphragm portion. This pump also requires spaces for fixing screws.
Accordingly, pumps can be configured within certain limits and it is difficult to remarkably shorten external dimensions of pumps without reducing volumes (displacements) of pumps in particular.